This invention relates to systems and methods for processing blood, e.g., for filtration, pheresis, or other diagnostic or therapeutic purposes.
There are many types of continuous and intermittent blood processing systems, each providing different therapeutic effects and demanding different processing criteria.
For example, hemofiltration emulates normal kidney activities for an individual whose renal function is impaired or lacking. During hemofiltration, blood from the individual is conveyed in an extracorporeal path along a semipermeable membrane, across which a pressure difference (called transmembrane pressure) exists. The pores of the membrane have a molecular weight cut-off that can thereby pass liquid and uremic toxins carried in blood. However, the membrane pores can not pass formed cellular blood elements and plasma proteins. These components are retained and returned to the individual with the toxin-depleted blood. Membranes indicated for hemofiltration are commercially available and can be acquired from, e.g., Asahi Medical Co. (Oita, Japan).
After hemofiltration, fresh physiologic fluid is supplied to toxin-depleted blood. This fluid, called replacement fluid, is buffered either with bicarbonate, lactate, or acetate. The replacement fluid restores, at least partially, a normal physiologic fluid and electrolytic balance to the blood. Usually, an ultrafiltration function is also performed during hemofiltration, by which liquid is replaced in an amount slightly less than that removed. Ultrafiltration decreases the overall fluid level of the individual, which typically increases, in the absence of ultrafiltration, due to normal fluid intake between treatment sessions.
Following hemofiltration, fluid balancing, and ultrafiltration, the blood is returned to the individual.
One aspect of the invention provides a layered fluid circuit. The circuit includes first and second panel sections formed from sealed sheets of flexible material. A pattern of seals is formed in the first panel section to define a first fluid circuit. A pattern of seals is formed in the second panel section to define a second fluid circuit. The flexible sheets are aligned to place the first and second panel sections in a relationship with the first fluid circuit overlaying the second fluid circuit.
According to another aspect of the invention, first and second sheets of flexible material are sealed to form the first and second panel sections. The flexible sheets are folded over to place the first and second panel sections in a reverse facing relationship, with the first fluid circuit overlaying the second fluid circuit.
In certain embodiments, at least one of the fluid circuits includes a defined operating region, such as an in-line clamping region that closes in response to an exterior force to occlude flow in the fluid circuit, or an in-line pump tube, or an in-line sensor region to transmit pressure to an exterior pressure sensor, or an in-line fluid holding compartment, or combinations thereof.
In one embodiment, both first and second fluid circuits include in-line clamping regions, which overlay each other. In this arrangement, the in-line clamping regions jointly close in response to an exterior force to occlude fluid flow in both the first and second fluid circuits.
In one embodiment, both the first and second fluid circuits include in-line fluid holding compartments, which overly each other. The overlaying compartments mutually form a two-compartment chamber.
In one embodiment, at least one length of flexible tubing extends from a panel section and is joined in fluid communication with one or both of the fluid circuits.
According to another aspect of the invention, the fluid circuits defined by the aligned or folded over sheets are carried within the confines of a tray.
In other embodiments, the tray includes one or more cut-out regions that expose operating regions of the fluid circuits, such as in-line clamping regions, or in-line pump tubes, or in-line sensor regions, or in-line fluid holding compartments, or combinations thereof.
Another aspect of the invention provides a fluid circuit for volumetrically balancing fluid. The fluid circuit comprises first and second sheets of flexible material sealed to form first and second panels. A pattern of seals formed in the first panel defines a first fluid circuit for handling out going fluid. The first fluid circuit includes a first in-line compartment to retain a volume of out going fluid. A pattern of seals formed in the second panel defines a second fluid circuit for handing in going fluid. The second fluid circuit includes a second in-line compartment to retain a volume of in going fluid. The flexible sheets are aligned to place the first and second panels in a relationship with the first in-line compartment overlaying the second in-line compartment to mutually form a two-compartment chamber. The two-compartment chamber displaces out going fluid from the first in-line compartment as in going fluid is conveyed into the second in-line compartment, and vice versa.
Another aspect of the invention provides a method for forming a layered fluid circuit. The method seals first and second sheets of flexible material to form first and second panel sections. The method forms a pattern of seals in the first panel section to define a first fluid circuit, and also forms a pattern of seals in the second panel section to define a second fluid circuit. The method aligns the flexible sheets to place the first and second panel sections in a relationship with the first fluid circuit overlaying the second fluid circuit.
In one embodiment, the aligned flexible sheets are placed into a tray for use.